6-methylsulfinylhexyl Isothiocyanate Research Articles

Benefits of Wasabi Supplements with 6-MSITC (6-Methylsulfinyl Hexyl Isothiocyanate) on Memory Functioning in Healthy Adults Aged 60 Years and Older: Evidence from a Double-Blinded Randomized Controlled Trial.

Cognitive functions decline with age. Declined cognitive functions negatively affect daily behaviors. Previous studies showed the positive effect of spices and herbs on cognition. In this study, we investigated the positive impact of wasabi, which is a traditional Japanese spice, on cognitive functions. The main bioactive compound of wasabi is 6-MSITC (6 methylsulfinyl hexyl isothiocyanate), which has anti-oxidant and anti-inflammatory functions. Anti-oxidants and anti-inflammatories have an important role in cognitive health. Therefore, 6-MSITC is expected to have positive effects on cognitive function. Previous studies showed the beneficial effects on cognitive functions in middle-aged adults. However, it is unclear that 6-MSITC has a positive effect on cognitive functions in healthy older adults aged 60 years and over. Here, we investigated whether 12 weeks' 6-MSITC intervention enhances cognitive performance in older adults using a double-blinded randomized controlled trial (RCT). Seventy-two older adults were randomly assigned to 6-MSITC or placebo groups. Participants were asked to take a supplement (6-MSITC or a placebo) for 12 weeks. We checked a wide range of cognitive performances (e.g., executive function, episodic memory, processing speed, working memory, and attention) at the pre- and post-intervention periods. The 6-MSITC group showed a significant improvement in working and episodic memory performances compared to the placebo group. However, we did not find any significant improvements in other cognitive domains. This study firstly demonstrates scientific evidence that 6-MSITC may enhance working memory and episodic memory in older adults. We discuss the potential mechanism for improving cognitive functions after 6-MSITC intake.

Oral administration of 6-methylsulfinylhexyl isothiocyanate extracted from wasabi is safe and improves the fatigue and sleep of healthy volunteers

BackgroundThis study aimed to conduct a preliminary evaluation of the effects of 6-methylsulfinylhexyl isothiocyanate (6-MSITC) contained in wasabi rhizomes on fatigue and sleep and to examine its safety through overdose study.MethodsA total of 20 healthy volunteers who were experiencing daily fatigue were given powder containing 6-MSITC (4.8 mg/day of 6-MSITC) extracted from wasabi for 4 weeks. Then, fatigue, sleep, autonomic nervous functioning, stress, and immunity were evaluated. In addition, an overdose safety study of the extract powder (up to 16 mg/day of 6-MSITC for 4 weeks) was performed with 30 healthy volunteers in a double-blind, placebo-controlled method.ResultsThe powder containing 6-MSITC did not improve fatigue after a mental task, but fatigue before the mental task, sleep, and mood were improved significantly after 4 weeks intake. No changes were observed in the autonomic nerve function, stress, or immune markers. In the overdose safety study, no changes in the parameters ​​or side effects were observed, and the results showed that high doses of the extract powder containing 6-MSITC is safe.ConclusionThis study confirmed the possibility that this powder extracted from wasabi that contains 6-MSITC might improve fatigue and sleep. However, because the effectiveness evaluation in this study was a single-arm, open-label study and there was no placebo control group, these points must be considered when interpreting the results. Safety was confirmed in an overdose study of more than three times the amount compared to that in the efficacy evaluation study. In the future, further research should be conducted on its effectiveness for treating fatigue and sleep problems.Trial registrationUMIN clinical trial registration system, UMIN000049913. Registered 27 December 2022 Retrospectively registered, https://center6.umin.ac.jp/cgi-open-bin/ctr/ctr_view.cgi?recptno=R000056818

Clinical effects of wasabi extract containing 6-MSITC on myalgic encephalomyelitis/chronic fatigue syndrome: an open-label trial

BackgroundWasabi (Eutrema japonicum) is a common pungent spice used in Japan. 6-Methylsulfinylhexyl isothiocyanate (6-MSITC) found in the rhizome of wasabi has been shown to have anti-inflammatory and antioxidant effects, as well as improve neuroinflammation and memory. Therefore, we hypothesized that these effects would be beneficial for treating myalgic encephalomyelitis/chronic fatigue syndrome (ME/CFS). The present study was conducted to investigate the effectiveness of wasabi extract containing 6-MSITC on ME/CFS in an open-label trial.MethodsFifteen patients (3 males, 12 females, 20–58 years old) were orally administered wasabi extract (9.6 mg of 6-MSITC/day) for 12 weeks. The following parameters and test results were compared pre- and post-treatment: performance status (PS), self-rating questionnaires, pressure pain threshold (PPT) on the occiput, Trail Making test-A (TMT-A), and hemodynamic patterns determined by an active standing test.ResultsAfter treatment with 6-MSITC, PS improved significantly (p = 0.001). Although the scores on the 11-item Chalder Fatigue scale (CFS-11) and numerical rating scale (NRS) of fatigue did not show significant changes, subjective symptoms improved significantly, including headache frequency (4.1 to 3.0 times/week, p = 0.001) and myalgia (4.1 to 2.4 times/week, p = 0.019), NRS brain fog scores (5.7 to 4.5, p = 0.011), difficulty finding appropriate words (4.8 to 3.7, p = 0.015), photophobia (4.8 to 3.5, p = 0.008), and the Profile of Mood Status vigor score (46.9 to 50.0, p = 0.045). The PPT of the right occiput (17.3 to 21.3 kPa, p = 0.01) and TMT-A scores (53.0 to 38.1 s, p = 0.007) also changed, suggesting reduced pain sensitivity, and improved cognitive function, respectively. Orthostatic patterns determined by a standing test did not show remarkable changes. There were no serious adverse reactions.ConclusionThis study suggests that 6-MSITC improves PS as well as subjective symptoms such as pain and cognitive dysfunction, and psychological vitality of patients with ME/CFS. It also improved cognitive performance and increased pain thresholds in these patients. 6-MSITC may be a promising therapeutic option especially for improving cognitive dysfunction associated with ME/CFS.

6-Methylsulfinylhexyl Isothiocyanate Inhibits Cell Cycle Progression in Quiescent Jb6 Cells Stimulated with Epidermal Growth Factor

Objective: The effects of 6-MSITC on cell cycle progression were investigated in quiescent mouse epidermal JB6 cells.
 Background: 6-Methylsulfinylhexyl isothiocyanate (6-MSITC) derived from wasabi (Wasabia japonica) has been reported to prevent tumor development in vivo.
 Material and methods: Treatment with epidermal growth factor (EGF) to quiescent JB6 cells, which were serum-starved for 36 h, promoted cell cycle progression from the G0/G1 phase to the S phase. Effects of pretreatment with 6-MSITC on cell cycle progression were estimated by flowcytometry and real-time RT-PCR.
 Results: Pretreatment with 6-MSITC at 0.25-1.0 μg/ml prior to the growth stimulation with EGF significantly inhibited cell cycle progression. Pretreatment with 6-MSITC inhibited the gene expression of DNA synthesis-related proteins cyclin A2, dumbbell former 4, and proliferating cell nuclear antigen.
 Conclusion: These results showed that 6-MSITC inhibits cell cycle progression in quiescent cells, accompanied by the inhibition of gene expression of DNA synthesis proteins.

Deacetylase Plus Bromodomain Inhibition Downregulates ERCC2 and Suppresses the Growth of Metastatic Colon Cancer Cells.

Simple SummaryIn cancer cells, the DNA repair response can be exploited as an ‘Achilles heel’ to trigger programmed cell death pathways and tumor elimination. Rather than involving ‘naked’ DNA, repair occurs in the context of histone and non-histone proteins in the vicinity of the damage. Drugs that target different epigenetic mechanisms can lead to the synergistic downregulation of critical DNA repair factors, including those associated with poor survival in colorectal cancer patients. Notably, normal colonic epithelial cells are more resistant than colon cancer cells to the epigenetic drug combinations. In the current investigation, cell-based assays and preclinical animal models reaffirmed the crosstalk between DNA repair and epigenetic regulatory mechanisms, and provided new avenues for precision oncology and cancer interception.There is growing evidence that DNA repair factors have clinical value for cancer treatment. Nucleotide excision repair (NER) proteins, including excision repair cross-complementation group 2 (ERCC2), play a critical role in maintaining genome integrity. Here, we examined ERCC2 expression following epigenetic combination drug treatment. Attention was drawn to ERCC2 for three reasons. First, from online databases, colorectal cancer (CRC) patients exhibited significantly reduced survival when ERCC2 was overexpressed in colon tumors. Second, ERCC2 was the most highly downregulated RNA transcript in human colon cancer cells, plus Ercc2 in rat tumors, after treatment with the histone deacetylase 3 (HDAC3) inhibitor sulforaphane (SFN) plus JQ1, which is an inhibitor of the bromodomain and extraterminal domain (BET) family. Third, as reported here, RNA-sequencing of polyposis in rat colon (Pirc) polyps following treatment of rats with JQ1 plus 6-methylsulfinylhexyl isothiocyanate (6-SFN) identified Ercc2 as the most highly downregulated gene. The current work also defined promising second-generation epigenetic drug combinations with enhanced synergy and efficacy, especially in metastasis-lineage colon cancer cells cultured as 3D spheroids and xenografts. This investigation adds to the growing interest in combination approaches that target epigenetic ‘readers’, ‘writers’, and ‘erasers’ that are deregulated in cancer and other pathologies, providing new avenues for precision oncology and cancer interception.

Stimulatory Effects of 6-Methylsulfinylhexyl Isothiocyanate on Cultured Human Follicle Dermal Papilla Cells

Stimulatory Effects of 6-Methylsulfinylhexyl Isothiocyanate on Cultured Human Follicle Dermal Papilla Cells

Inhibitory Effects of 6-Methylsulfinylhexyl Isothiocyanate on Superoxide Anion Generation from Differentiated HL-60 Human Promyelocytic Leukemia Cells

Wasabi is a plant of Japanese origin. It belongs to the Brassicaceae family and produces various isothiocyanates (ITCs). Because 6-methylsulfinylhexyl isothiocyanate (6-MSITC) is particularly stable among wasabi ITCs, it has potential as a functional compound. To clarify the antioxidative activity of 6-MSITC, we investigated its inhibitory effect on superoxide anion (O2•−) generation from phorbol 12-myristate 13-acetate (PMA)-stimulated differentiated HL-60 human promyelocytic leukemia cells. Our results showed that 6-MSITC inhibited O2•− generation in these cells (IC50 value: 28.9 µM). 6-MSITC at 0.8, 4, and 20 µM significantly inhibited the consumption of exogenously added NADH compared with the control. On the other hand, < 263 µM 6-MSITC did not scavenge O2•− in cell-free experiments. Therefore, we suggest that 6-MSITC inhibited O2•− generation by decreasing an enzymatic reaction with NADPH oxidase. Thus, 6-MSITC may be useful as a functional compound.

6‐Methylsulfinylhexyl isothiocyanate prevents high‐fat diet‐induced fatty liver but fails to attenuate hepatic iron accumulation in mice

6-Methylsulfinylhexyl isothiocyanate (6-MSITC) is a bioactive ingredient present in Japanese horseradish (wasabi) and has been shown to be an Nrf2 activator. To determine whether 6-MSITC ameliorates hepatic steatosis and iron accumulation, wild-type and Nrf2-null mice were fed the following diets for 12 weeks: 1) control diet, 2) high-fat diet (HFD), 3) HFD plus 6-MSITC (10mg/Kg/day ip), 4) HFD for 6 weeks followed by an iron-supplemented HFD for 6 weeks (HFD/Iron), 5) HFD/Iron plus 6-MSITC. The HFD increased hepatic triglycerides in both genotypes and 6-MSITC suppressed increased hepatic triglycerides in wild-type mice but did not reduce these triglycerides in Nrf2-null mice. Compared to the HFD and HFD/Iron groups, respectively, 6-MSITC did not block hepatic iron accumulation in either genotype. This article is protected by copyright. All rights reserved.

Sulforaphane homologues: Enantiodivergent synthesis of both enantiomers, activation of the Nrf2 transcription factor and selective cytotoxic activity

Reported is an enantiodivergent approach for the synthesis of both enantiomers of sulforaphane (SFN) homologues with different chain lengths between the sulfinyl sulfur and the isothiocyanate groups and different substituents on the sulfinyl sulfur. The homologues were designed in order to unravel the effect of all the diversity elements included in sulforaphane's structure. The key step of the approach is the diastereoselective synthesis of both sulfinate ester epimers at sulfur, using as single chiral auxiliary the sugar derived diacetone-d-glucose. The approach allows the first synthesis of both enantiomers of 5-methylsulfinylpentyl isothiocyanate, and the biologically important 6-methylsulfinylhexyl isothiocyanate (6-HITC) found in Japanese horseradish, wasabi (Wasabia japonica). The ability of the synthesized compounds as inductors of phase II detoxifying enzymes has been studied by determining their ability to activate the cytoprotective transcription factor Nrf2. The cytotoxic activity of all the synthesized compounds against human lung adenocarcinoma (A549) and foetal lung fibroblasts (MRC-5) is also reported.

6-Methylsulfinylhexyl isothiocyanate modulates endothelial cell function and suppresses leukocyte adhesion

6-Methylsulfinylhexyl isothiocyanate (6-MSITC) is an active compound in wasabi (Wasabia japonica Matsum.), which is one of the most popular spices in Japan. 6-MSITC suppresses lipopolysaccharide-induced macrophage activation, arachidonic- or adenosine diphosphate-induced platelet activation, and tumor cell proliferation. These data indicate that 6-MSITC has several biological activities involving anti-inflammatory, anti-coagulant, and anti-apoptosis properties. Endothelial cells (ECs) maintain vascular homeostasis and play crucial roles in crosstalk between blood coagulation and vascular inflammation. In this study, we determined the anti-coagulant and anti-inflammatory effects of 6-MSITC on human umbilical vein endothelial cells (HUVECs). 6-MSITC slightly reduced tissue factor expression, but did not alter von Willebrand factor release in activated HUVECs. 6-MSITC modulated the generation of activated protein C, which is essential for negative regulation of blood coagulation, on normal ECs. In addition, 6-MSITC reduced tumor necrosis factor-α (TNF-α)-induced interleukin-6 and monocyte chemoattractant protein-1 expression. 6-MSITC markedly attenuated TNF-α-induced adhesion of human monoblast U937 cells to HUVECs and reduced vascular cell adhesion molecule-1 and E-selectin mRNA expression in activated ECs. These results showed that 6-MSITC modulates EC function and suppresses cell adhesion. This study provides new insight into the mechanism of the anti-inflammatory effect of 6-MSITC, suggesting that 6-MSITC has therapeutic potential as a treatment for vasculitis and vascular inflammation.

Transthiocarbamoylation of Proteins by Thiolated Isothiocyanates

Isothiocyanates, membrane-permeable electrophiles that form adducts with thiols, have been suggested to have important medical benefits. Here we shed light on isothiocyanate-thiol conjugates and studied their electrophilic potential transferring an isothiocyanate moiety to cellular proteins. When we examined the effect of sulfhydryl molecules on cellular response induced by 6-methylsulfinylhexyl isothiocyanate (6-HITC), an analog of sulforaphane isolated from broccoli, we observed significant induction of heme oxygenase-1 by 6-HITC even in the presence of N-acetyl-L-cysteine or glutathione (GSH). In addition, the authentic 6-HITC-β-mercaptoethanol (6-HITC-ME) conjugate markedly up-regulated the enzyme expression, suggesting the electrophilic potential of thiolated isothiocyanates. To gain a chemical insight into the cellular response induced by thiolated isothiocyanates, we studied the occurrence of transthiocarbamoylation of sulfhydryl molecules by 6-HITC-ME and observed that, upon incubation of 6-HITC-ME with GSH, a single product corresponding to the GSH conjugate of 6-HITC was generated. To test the functional ability of thiolated isothiocyanates to thiocarbamoylate proteins in living cells, we designed a novel probe, combining an isothiocyanate-reactive group and an alkyne functionality, and revealed that the transthiocarbamoylation of proteins occurred in the cells upon exposure to 6-HITC-ME. The target of thiocarbamoylation included heat shock protein 90 β (Hsp90β), a chaperone ATPase of the Hsp90 family implicated in protein maturation and targeting. To identify the sites of the Hsp90β modification, we utilized nano-LC/MALDI-TOF MS/MS and suggested that a thiol group on the peptide containing Cys-521 reacted with 6-HITC, resulting in a covalent adduct in a 6-HITC-treated recombinant Hsp90β in vitro. The site-selective binding to Cys-521 was supported by in silico modeling. Further study on the thiocarbamoylation of Hsp90β suggested that the formation of 6-HITC-Hsp90β conjugate might cause activation of heat shock factor-1, rapidly signaling a potential heat shock response. These data suggest that thiolated isothiocyanates are an active metabolite that could contribute to cellular responses through transthiocarbamoylation of cellular proteins.

Isothiocyanates Reduce Mercury Accumulation via an Nrf2-Dependent Mechanism during Exposure of Mice to Methylmercury

Background: Methylmercury (MeHg) exhibits neurotoxicity through accumulation in the brain. The transcription factor Nrf2 (nuclear factor erythroid 2-related factor 2) plays an important role in reducing the cellular accumulation of MeHg.Objectives: We investigated the protective effect of isothiocyanates, which are known to activate Nrf2, on the accumulation of mercury after exposure to MeHg in vitro and in vivo.Methods: We used primary mouse hepatocytes in in vitro experiments and mice as an in vivo model. We used Western blotting, luciferase assays, atomic absorption spectrometry assays, and MTT [3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] assays, and we identified toxicity in mice based on hind-limb flaccidity and mortality.Results: The isothiocyanates 6-methylsulfinylhexyl isothiocyanate (6-HITC) and sulforaphane (SFN) activated Nrf2 and up-regulated downstream proteins associated with MeHg excretion, such as glutamate-cysteine ligase, glutathione S-transferase, and multidrug resistance–associated protein, in primary mouse hepatocytes. Under these conditions, intracellular glutathione levels increased in wild-type but not Nrf2-deficient primary mouse hepatocytes. Pretreatment with 6-HITC and SFN before MeHg exposure suppressed cellular accumulation of mercury and cytotoxicity in wild-type but not Nrf2-deficient primary mouse hepatocytes. In comparison, in vivo administration of MeHg to Nrf2-deficient mice resulted in increased sensitivity to mercury concomitant with an increase in mercury accumulation in the brain and liver. Injection of SFN before administration of MeHg resulted in a decrease in mercury accumulation in the brain and liver of wild-type, but not Nrf2-deficient, mice.Conclusions: Through activation of Nrf2, 6-HITC and SFN can suppress mercury accumulation and intoxication caused by MeHg intake.

Immunochemical Detection of Food-Derived Isothiocyanate as a Lysine Conjugate

In a previous study we prepared monoclonal antibody against allyl isothiocyanate (AITC)-modified lysine (Lys), and found that AITC reacted with Lys under physiological conditions in vitro (T. Nakamura et al., Chem. Res. Toxicol., 22, 536-542 (2009)). In the present study, antibodies against benzyl isothiocyanate (ITC), 6-methylsulfinylhexyl ITC and phenethyl ITC modified protein were prepared, and the respective monoclonal antibodies, B6C9, 6MS3D10, and PE3A10 were obtained. These antibodies were applied to ITC detection in food using shredded Wasabia japonica (wasabi) and ground Carica papaya (papaya) seed by trapping ITC with biotin-labeled bovine serum albumin. ITC formation from the wasabi and papaya seed samples was confirmed using the antibodies in a dose-dependent manner. These antibodies might be applicable in identifying food-derived ITC.

Chemoprevention of 1,2-dimethylhydrazine-induced colonic preneoplastic lesions in Fischer rats by 6-methylsulfinylhexyl isothiocyanate, a wasabi derivative

The preventive effects of dietary exposure to a wasabi derivative 6-methylsulfinylhexyl isothiocyanate (6-MSITC) during the initiation and post-initiation phases on the development of 1,2-dimethylhydrazine (DMH)-induced colonic aberrant crypt foci (ACF), and β-catenin-accumulated crypts (BCAC) were investigated in male F344 rats. To induce ACF and BCAC, rats were given four weekly subcutaneous injections of DMH (40 mg/kg body weight). The rats also received diets containing 200 or 400 ppm 6-MSITC during the initiation or post-initiation phases. The experiment was terminated 12 weeks after the start. DMH exposure produced a substantial number of ACF (323.8±69.7/colon) and BCAC (3.80±1.05/cm(2)) at the end of the study. Dietary administration of 6-MSITC at a dose of 400 ppm during the initiation phase caused a significant reduction in the total number of ACF (52% reduction, P<0.0001), larger ACF (4 or more crypt ACF) (58% reduction, P<0.001) and BCAC (76% reduction, P<0.00001). The dietary exposure to 6-MSITC significantly reduced the size (crypt multiplicity) of BCAC during both initiation and post-initiation treatment when compared to group 1 treated with DMH alone. Immunohistochemically, 6-MSITC administration lowered the proliferating cell nuclear antigen labeling index in ACF and BCAC. In addition, protein levels of hepatic cytochrome P-450 isozymes at 24 h after 6-MSITC exposure were significantly suppressed (P<0.01). The results indicated that 6-MSITC exerted chemopreventive effects in the present short-term colon carcinogenesis bioassay, through alterations in cell proliferation activity and drug metabolizing enzyme levels.

A food‐derived synergist of NGF signaling: identification of protein tyrosine phosphatase 1B as a key regulator of NGF receptor‐initiated signal transduction

Neurotrophins, such as the nerve growth factor (NGF), play an essential role in the growth, development, survival and functional maintenance of neurons in the central and peripheral systems. They also prevent neuronal cell death under various stressful conditions, such as ischemia and neurodegenerative disorders. NGF induces cell differentiation and neurite outgrowth by binding with and activating the NGF receptor tyrosine kinase followed by activation of a variety of signaling cascades. We have investigated the NGF-dependent neuritogenesis enhancer potential of a food-derived small molecule contained in Brassica vegetables and identified the protein tyrosine phosphatase (PTP) 1B as a key regulator of the NGF receptor-initiated signal transduction. Based on an extensive screening of Brassica vegetable extracts for the neuritogenic-promoting activity in the rat pheochromocytoma cell line PC12, we found the Japanese horseradish, wasabi (Wasabia japonica, syn. Eutrema wasabi), as the richest source and identified 6-methylsulfinylhexyl isothiocyanate (6-HITC), an analogue of sulforaphane isolated from broccoli, as one of the major neuritogenic enhancers in the wasabi. 6-HITC strongly enhanced the neurite outgrowth and neurofilament expression elicited by a low-concentration of NGF that alone was insufficient to induce neuronal differentiation. 6-HITC also facilitated the sustained-phosphorylation of the extracellular signal-regulated kinase and the autophosphorylation of the NGF receptor TrkA. It was found that PTP1B act as a phosphatase capable of dephosphorylating Tyr-490 of TrkA and was inactivated by 6-HITC in a redox-dependent manner. The identification of PTP1B as a regulator of NGF signaling may provide new clues about the chemoprotective potential of food components, such as isothiocyanates.

Effects of dietary chemopreventive phytochemicals on P-glycoprotein function

The effects of dietary phytochemicals on P-glycoprotein function were investigated using human multidrug-resistant carcinoma KB-C2 cells and the fluorescent P-glycoprotein substrates daunorubicin and rhodamine 123. The effects of natural chemopreventive compounds, capsaicin found in chilli peppers, curcumin in turmeric, [6]-gingerol in ginger, resveratrol in grapes, sulforaphane in broccoli, 6-methylsulfinyl hexyl isothiocyanate (6-HITC) in Japanese horseradish wasabi, indole-3-carbinol (I3C) in cabbage, and diallyl sulfide and diallyl trisulfide in garlic, were examined. The accumulation of daunorubicin in KB-C2 cells increased in the presence of capsaicin, curcumin, [6]-gingerol, and resveratrol in a concentration-dependent manner. The accumulation of rhodamine 123 in KB-C2 cells was also increased, and the efflux of rhodamine 123 from KB-C2 cells was decreased by these phytochemicals. Sulforaphane, 6-HITC, I3C, and diallyl sulfide and diallyl trisulfide had no effect. These results suggest that dietary phytochemicals, such as capsaicin, curcumin, [6]-gingerol, and resveratrol, have inhibitory effects on P-glycoprotein and potencies to cause drug–food interactions.

6-Methylsulfinylhexyl Isothiocyanate, an Antioxidant Derived from Wasabia japonica MATUM, Ameliorates Diabetic Nephropathy in Type 2 Diabetic Mice

Many studies have examined the protective effects of antioxidative agents against diabetic nephropathy, using various models. 6-Methylsulfinylhexyl isothiocyanate (6-MSITC) isolated from wasabi (Wasabia japonica MATUM) induces glutathione S-transferase in vitro, thus 6-MSITC may act as an antioxidant in vivo. The aim of this study was to examine whether wasabi powder (WP) and 6-MSITC suppress oxidative stress in vivo and inhibit the impairment of renal function and diabetic nephropathy, using type 2 diabetic mice. KK-Ay type 2 diabetic mice were assigned to three groups (n = 10 each); control mice were fed normal chow (CRF-1) and two experimental groups were fed CRF-1 containing 0.5% WP or 0.03% 6-MSITC for 4 wk. Urine volume, urinary albumin excretion, and creatinine clearance were significantly lower in the 6-MSITC group than in the control group. There was statistically no difference in TBARS or other biomarkers of oxidative stress among the three groups. However, urinary 8-hydroxy-2′-deoxyguanosine (8-OHdG), one of the markers of oxidative stress tended to be lower in the 6-MSITC group than in the control group. In conclusion, the present results show that a sufficient supply of dietary 6-MSITC may prevent or delay renal dysfunction in diabetes by protecting against oxidative stress, and that dietary 6-MSITC may have beneficial effects on diabetic complications in type 2 diabetic mice.

Identification of 6-methylsulfinylhexyl isothiocyanate as an apoptosis-inducing component in wasabi

The ethanol extract from Japanese horseradish wasabi was found to inhibit cell proliferation in human monoblastic leukemia U937 cells by inducing apoptotic cell death. Separation by methods including silica gel chromatography and preparative HPLC gave an active compound, which was identified as 6-methylsulfinylhexyl isothiocyanate (6-HITC). Several lines of evidence indicated that 6-HITC induced apoptosis in U937 cells and human stomach cancer MKN45 cells. Thus, 6-HITC is potentially useful as a natural anti-cancer agent.

A Sulforaphane Analogue That Potently Activates the Nrf2-dependent Detoxification Pathway

Exposure of cells to a wide variety of chemoprotective compounds confers resistance to a broad set of carcinogens. For a subset of the chemoprotective compounds, protection is generated by an increase in the abundance of the protective phase II detoxification enzymes, such as glutathione S-transferase (GST). We have recently developed a cell culture system, using rat liver epithelial RL 34 cells, that potently responds to the phenolic antioxidants resulting in the induction of GST activity (Kawamoto, Y., Nakamura, Y., Naito, Y., Torii, Y., Kumagai, T., Osawa, T., Ohigashi, H., Satoh, K., Imagawa, M., and Uchida, K. (2000) J. Biol. Chem. 275, 11291-11299.) In the present study, we investigated the phase II-inducing potency of an isothiocyanate compound in vitro and in vivo and examined a possible induction mechanism. Based on an extensive screening of vegetable extracts for GST inducer activity in RL34 cells, we found Japanese horseradish, wasabi (Wasabia japonica, syn. Eutrema wasabi), as the richest source and identified 6-methylsulfinylhexyl isothiocyanate (6-HITC), an analogue of sulforaphane (4-methylsulfinylbutyl isothiocyanate) isolated from broccoli, as the major GST inducer in wasabi. 6-HITC potently induced both class alpha GSTA1 and class pi GSTP1 isozymes in RL34 cells. In animal experiments, we found that 6-MSHI was rapidly absorbed into the body and induced hepatic phase II detoxification enzymes more potently than sulforaphane. The observations that (i) 6-HITC activated the antioxidant response element (ARE), (ii) 6-HITC induced nuclear localization of the transcription factor Nrf2 that binds to ARE, and (iii) the induction of phase II enzyme genes by 6-HITC was completely abrogated in the nrf2-deficient mice, suggest that 6-HITC is a potential activator of the Nrf2/ARE-dependent detoxification pathway.

Antiplatelet and anticancer isothiocyanates in Japanese domestic horseradish, Wasabi

6-Methylsulfinylhexyl isothiocyanate (MS-ITC) was isolated from wasabi ( Wasabia japonica, Japanese domestic horseradish) as a potential inhibitor of human platelet aggregation in vitro through our extensive screening of vegetables and fruits. In the course of an another screening for the induction of glutathione S-transferase (GST) activity in RL34 cells, MS-ITC was inadvertently isolated from wasabi as a potential inducer of GST. MS-ITC administered to rats or mice also showed both activities in vivo. As a result from elucidation of the platelet aggregation inhibition and the GST induction mechanisms of MS-ITC, the isothiocyanate moiety of MS-ITC plays an important role for antiplatelet and anticancer activities because of its high reactivity with sulfhydryl (RSH) groups in biomolecules (GSH, cysteine residue in a certain protein, etc.).